Growing of potato microplants in the presence of alginate-silverthiosulfate capsules reduces ethylene-induced culture abnormalities during minimal growth conservation in vitro

Alginate capsules containing anionic complex silverthiosulfate (STS) [Ag(S2 O3)(2)(3-)] were placed in the culture tubes over minimal growth media for studying whether STS could be used at higher concentrations to sustain ethy lene-inhibiting effect during conservation of microplants in six potato (So lanum tuberosum L.) genotypes in vitro. Different concentrations of STS (0. 1, 0.5, 1.0, 2.0, 3.0 and 4.0 mM) were incorporated into the alginate capsu les, and 12 alginate-STS capsules were tested in semisolid (7 g l(-1) agar) minimal growth medium containing 20 g l(-1) mannitol and 40 g l(-1) sucros e. This indirect supplementation of STS through alginate capsules rendered reduced total availability of STS in the minimal growth medium as compared to when it was directly supplemented in the medium at a given concentration . Growing of microplants in the presence of alginate-STS capsules improved the microplant growth and reduced the culture abnormalities over a period o f 16 months under minimal growth conditions. Most significant improvement i n microplant growth was in terms of green leaf production and leaf senescen ce. Vitrification, flaccidity and other growth abnormalities, viz., leaf lo ss, abnormal stem swelling and necrosis were not observed when the micropla nts were conserved in the presence of alginate-STS capsules. To foster opti mum microplant growth and reduce culture abnormalities, potato microplants could favourably be maintained in the presence of 0.5-1.0 mM alginate-STS c apsules during minimal growth conservation. Higher concentrations of algina te-STS capsules (>1.0 mM) were in general detrimental to potato microplant growth and survival during prolonged storage in vitro. Release kinetics of STS from the alginate-STS capsules, its distribution in the medium and accu mulation of silver in potato microplants were studied using (110)mAg. The r elease rate of STS from the capsules was found to be directly proportional to the concentrations of alginate-STS capsules. A distinct concentration gr adient of (110)mAg in the medium with increasing depth from top to bottom, and its accumulation in the potato microplants may be attributed to the imp roved anti-ethylene action of STS at higher concentrations through alginate capsules.